FORM 5

CHAPTER 1: TRANSPORT SYSTEM

The Heart

The heart is a 4 chambered double pump, responsible of circulating oxygenated blood around the body and deoxygenated blood to the lungs. An adult heart pumps about 5 litres of blood per minute. The heart, has 2 upper chambers called atria (singular: Atrium) and 2 lower chambers called ventricles. The heart has 2 pumps
and circulates oxygenated and de-oxygenated blood. This is known as double circulation.

Aorta: The largest artery found in the body. It receives oxygenated blood from the heart and then divides into many arteries all around the body.
Vena Cava: The largest vein found in the body. It transports de-oxygenated blood to the heart from the rest of the body. De-oxygenated blood is then transported to the lungs to be oxygenated.
Atrium: One of the upper chambers of the heart.
Tricuspid valve: A valve that lets blood to pass from the right atrium to the right ventricle.
Ventricle: one of the lower chambers of the heart.
Bicuspid valve: the valve that lets blood to pass from the left atrium to the left ventricle.
Pulmonary Vein: The vein that carries oxygenated blood to the left atrium.
Semi-lunar valves: the 2 valves which let blood pass from the lower ventricle to the aorta and the pulmonary artery.
Pulmonary Artery: The artery that carries deoxygenated blood from the heart to the lungs.

The Difference between Arteries and Veins
The main difference between arties and veins is that arteries carry blood from the heat to all the other tissues in the body while veins carry blood from the body to the heart. Usually, veins carry deoxygenated blood and arteries carry oxygenated blood. One exception is that the pulmonary artery carries deoxygenated blood from the body to the heart and the pulmonary vein carry oxygenated blood from the heart to the lungs. Veins have valves so that blood goes in the right direction; arteries don’t have valves because blood flows with a lot of pressure inside the arteries and backflow of blood is impossible. Arteries have a thin lumen (inner structure of the blood vessel, where blood passes) because blood flows with a high pressure and the walls have to be wide, while veins have a wide lumen. Arteries have an elastic wall, but veins don’t have an elastic wall.